1. Field of the Invention
The present invention relates to antibodies which bind to human tissue factor, including specified portions or variants thereof. The antibodies of the invention have the ability to interact with effector cells to activate innate immunity in addition to their human tissue factor neutralizing activity and are thus particularly useful in methods for treating tumor cells. The invention also relates to nucleic acids encoding such anti-tissue factor antibodies, complementary nucleic acids, vectors, host cells, and methods of making and using thereof, including therapeutic formulations, administration and devices.
2. Related Art
Tissue Factor (TF)
The coagulation of blood involves a cascading series of reactions leading to the formation of fibrin. The coagulation cascade consists of two overlapping pathways, both of which are required for hemostasis. The intrinsic pathway comprises protein factors present in circulating blood, while the extrinsic pathway requires tissue factor (TF), which is expressed on the cell surface of a variety of tissues in response to vascular injury (Davie et al., 1991, Biochemistry 30:10363). When exposed to blood, TF sets in motion a potentially explosive cascade of activation steps that result in the formation of an insoluble fibrin clot. TF has been investigated as a target for anticoagulant therapy.
TF is a single chain, 263 amino acid membrane glycoprotein that functions as a receptor for factor VII and VIIa and thereby initiates the extrinsic pathway of the coagulation cascade in response to vascular injury. TF is a transmembrane cell surface receptor which serves as the receptor as well as the cofactor for factor VIIa, forming a proteolytically active TF:VIIa complex on cell surfaces (Ruf et al, (1992) J. Biol. Chem 267:6375-6381). In addition to its role in maintaining hemostasis, excess TF has been implicated in pathogenic conditions. Specifically, the synthesis and cell surface expression of TF has been implicated in vascular disease (Wilcox et al., 1989, Proc. Natl. Acad. Sci, 86:2839) and gram-negative septic shock (Warr et al., 1990, Blood 75:1481).
TF Antagonists
Various anti-TF antibodies are known. For example, Carson et al, (1987, Blood 70:490-493) discloses a hybridoma producing monoclonal antibody prepared by immunizing mice with TF purified by affinity chromatography on immobilized factor VII. Ruf et al, (1991, Thrombosis and Haemostasis 66:529) characterized the anticoagulant potential of murine monoclonal antibodies against human TF. The ability of monoclonal antibodies that target the FVII binding site on TF, is dependent on their ability to compete with FVII for binding to TF and formation of the TF/VIIa complex, which is rapidly formed when TF contacts plasma. Such antibodies were thus relatively slow inhibitors of TF in plasma. One monoclonal antibody, TF8-5G9, was capable of inhibiting the TF/VIIa complex, thus providing an immediate anticoagulant effect in plasma. This antibody is disclosed in U.S. Pat. Nos. 6,001,978, 5,223,427, and 5,110,730. Ruf et al, suggested (supra) that mechanisms that inactivate the TF/VIIa complex, rather than prevent its formation, may provide strategies for interruption of coagulation in vivo. In contrast to other antibodies that inhibit factor VII binding to TF, TF8-5G9 shows only subtle and indirect effects on factor VII or factor VIIa binding to the receptor. TF8-5G9 binds to the extracellular domain of TF with a nanomolar binding constant to block the formation of the TF:F.VIIa:F.X ternary initiation complex (Huang et al, J. Mol. Biol. 275:873-894 1998).
Anti-TF monoclonal antibodies have been shown to inhibit TF activity in various species (Morissey et al., 1988, Thromb. Res. 52:247-260) and neutralizing anti-TF antibodies have been shown to prevent death in a baboon model of sepsis (Taylor et al, Circ. Shock, 33:127 (1991)), and attenuate endotoxin induced DIC in rabbits (Warr et al, (1990) Blood 75:1481).
WO 96/40921 discloses CDR-grafted anti-TF antibodies derived from the TF8-5G9 antibody. Other humanized or human anti-TF antibodies are disclosed in Presta et al, Thromb Haemost 85:379-389 (2001), EP1069185, WO 01/70984 and WO03/029295.
The Role of TF in Cancer
Tissue factor (TF) is a cell surface receptor best known for its role in initiating blood coagulation upon injury. Tissue factor is also overexpressed on a variety of malignant tumors and isolated human tumor cell lines, suggesting a role in tumor growth and survival. TF is not produced by healthy endothelial cells lining normal blood vessels but is expressed on these cells in tumor vessels. It appears to play a role in both vasculogenesis, the formation of new blood vessels in the developing animal and in angiogenesis, the sprouting of new capillaries from existing arteries, in normal and malignant adult tissues.
Aberrant expression of TF on endothelial and tumor cells in a variety of breast, colorectal, lung and pancreatic cancers has been linked to an increase in tumor microvessel density and upregulated VEGF expression. Tumor cells over expressing TF are also thought to be responsible for the thrombotic complications associated with cancer. Thus there is a rationale for the inhibition of tissue factor in the treatment of cancer.
WO94/05328 discloses the use of anti-TF antibodies to inhibit the onset and progression of metastasis by abolishing the prolonged adherence of metastazing cells in the microvasculature thereby inhibiting metastasis, but does not disclose any effect on the growth of established tumor cells. Given the complexity in the factors regulating tumor vascularization as well as the incomplete understanding of the role of tissue factor as a receptor mediating cellular growth in both tumor growth and wound healing, it is possible that blockade of TF could play either a critical or a redundant role in the pathogenesis of cancer or other diseases characterized by inappropriate angiogenic activity. Inhibition or targeting of TF may therefore be a useful anti-tumor strategy that could affect the survival of TF overexpressing tumor cells directly by inhibiting TF mediated cellular signaling or other activities. In addition, this approach may prevent tumor growth indirectly via an antiangiogenic mechanism by inhibiting the growth or function of TF expressing intra-tumoral endothelial cells.
TF and Angiogenesis
Angiogenesis is the process of generating new capillary blood vessels, and results from activated proliferation of endothelial cells. Neovascularization is tightly regulated, and occurs only during embryonic development, tissue remodeling, wound healing and periodic cycle of corpus luteum development (Folkman and Cotran, Relation of vascular proliferation to tumor growth, Int. Rev. Exp. Pathol. '16, 207-248 (1976)).
There is now considerable evidence that tumor growth and cancer progression requires angiogenesis and neovascularization, blood vessel growth and extension, in order to provide tumor tissue with nutrients and oxygen, to carry away waste products and to act as conduits for the metastasis of tumor cells to distant sites (Folkman, et al. N Engl J Med 285: 1181-1186, 1971 and Folkman, et al. N Engl J Med 333: 1757-1763, 1995). Nevertheless, tissue and tumor angiogenesis and neovascularization represent complex processes mediated by the interplay of cellularly produced factors: including TNFalpha, VEGF, and tissue factor. Studies show that the pathways leading to upregulation of VEGF and TF overlap (Chen J. et al. (2001) Thromb. Haemost. 86-334-5), two major players in the initiation of new blood vessel formation.
Endothelial cells normally proliferate much more slowly than other types of cells in the body. However, if the proliferation rate of these cells becomes unregulated, pathological angiogenesis can result. Pathological angiogenesis is involved in many diseases. For example, cardiovascular diseases such as angioma, angiofibroma, vascular deformity, atherosclerosis, synechia and edemic sclerosis; and opthalmological diseases such as neovascularization after cornea implantation, neovascular glaucoma, diabetic retinopathy, angiogenic corneal disease, macular degeneration, pterygium, retinal degeneration, retrolental fibroplasias, and granular conjunctivitis are related to angiogenesis. Chronic inflammatory diseases such as arthritis; dermatological diseases such as psoriasis, telangiectasis, pyogenic granuloma, seborrheic dermatitis, venous ulcers, acne, rosacea (acne rosacea or erythematosa), warts (verrucas), eczema, hemangiomas, lymphangiogenesis are also angiogenesis-dependent.
Vision can be impaired or lost because of various ocular diseases in which the vitreous humor is infiltrated by capillary blood. Diabetic retinopathy can take one of two forms, non-proliferative or proliferative. Proliferative retinopathy is characterized by abnormal new vessel formation (neovascularization), which grows on the vitreous surface or extends into the vitreous cavity. In advanced disease, neovascular membranes can occur, resulting in a traction retinal detachment. Vitreous hemorrhages may result from neovascularization. Visual symptoms vary. A sudden severe loss of vision can occur when there is intravitreal hemorrhage. Visual prognosis with proliferative retinopathy is more guarded if associated with severe retinal ischemia, extensive neovascularization, or extensive fibrous tissue formation. Macular degeneration, likewise takes two forms, dry and wet. In exudative macular degeneration (wet form), which is much less common, there is formation of a subretinal network of choroidal neovascularization often associated with intraretinal hemorrhage, subretinal fluid, pigment epithelial detachment, and hyperpigmentation. Eventually, this complex contracts and leaves a distinct elevated scar at the posterior pole. Both forms of age-related macular degeneration are often bilateral and are preceded by drusen in the macular region. Another cause of loss of vision related to angiogenic etiologies are damage to the iris. The two most common situations that result in the iris being pulled up into the angle are contraction of a membrane such as in neovascular glaucoma in patients with diabetes or central retinal vein occlusion or inflammatory precipitates associated with uveitis pulling the iris up into the angle (Ch. 99. The Merck Manual 17th Ed. 1999).
Rheumatoid arthritis, an inflammatory disease, also results in inappropriate angiogenesis. The growth of vascular endothelial cells in the synovial cavity is activated by the inflammatory cytokines, and results in cartilage destruction and replacement with pannus in the articulation (Koch A K, Polyerini P J and Leibovich S J. Arthritis Rheum. 29, 471-479 (1986); Stupack D G, Storgard C M and Cheresh D A, Braz. J. Med. Biol. Res., 32, 578-581 (1999); Koch A K, Arthritis Rheum, 41, 951 962 (1998)).
Psoriasis is caused by uncontrolled proliferation of skin cells. Fast growing cells require sufficient blood supply, and abnormal angiogenesis is induced in psoriasis (Folkman J., J. Invest. Dermatol., 59, 40-48 (1972)).
Antibody Properties
IgG1 and IgG4 antibody isotypes differ in their ability to mediate complement dependent cytotoxicity (CDC) and antibody-dependent cellular cytotoxicity (ADCC). CDC is the lysing of a target in the presence of complement. The complement activation pathway is initiated by the binding of the first component of the complement system (Clq) to a molecule complexed with a cognate antigen. IgG1 is a strong inducer of the complement cascade and subsequent CDC activity, while IgG4 has little complement-inducing activity.
ADCC is a cell-mediated reaction in which nonspecific cytotoxic cells that express Fc receptors (FcRs) (e.g., Natural Killer (NK) cells, neutrophils, and macrophages) recognize bound antibody on a target cell and subsequently cause lysis of the target cell. The IgG1 isotype subclass binds with high affinity to the Fc receptor and contributes to ADCC while IgG4 binds only weakly. The relative inability of IgG4 to activate effector functions is drawback in those applications such as oncology where cell killing is a desirable characteristic of the antibody.
There remains a need in the art for variant structures of anti-TF antibodies with properties optimized for specific clinical indications. For example, optimizing ADCC and CDC antibody functions is generally desirable for oncology indications. Other potential uses for anti-TF antibodies with enhanced ADCC activity include therapy for age related macular degeneration or other angiogenesis related conditions in which endothelial cells in aberrant blood vessels may express TF and can be targeted by ADCC. The inventors of this application have produced variant anti-TF antibody structures designed to meet these needs.